Amplifying stringed instrument



1938- R. w. ROBERTSON 2,139,099

AMPLIFYING ST LIETGED INSTRUMENT Filed June 5, 1937 mlllllllllmllmfl INVENTOR 64134 M FUSE/Q7150 ATTORNEYS.

Patented Dec. 6, 1938 UNITED STATES PATENT OFFICE 6 Claims.

This invention relates to improvements in stringed instruments, and particularly to that class of stringed instruments wherein it is desired to amplify the sounds produced by the instrument.

The invention is applicable to practically all types of stringed instruments but is particularly applicable to stringed instruments of the guitar, mandolin, and ukulele type.

It is an object of the invention to provide a stringed instrument with a suit-able resonator such as for example, a conical paper or composition cone which is disposed Within the body of the instrument and which is outwardly connected to the bridge of the instrument so that sound vibrations transmitted to the bridge by the vibrating strings will be transmitted to the resonator or cone and amplified.

Another object of the invention is to provide 20 an improved bridge construction for stringed instruments wherein there is a bridge-providing member pivotally connected to the body of the instrument and which has the strings of the instrument connected thereto. The bridge-providing member provides a bridge so arranged that it is urged by the tension of the strings themselves into engagement with the strings.

Another object of the invention is to provide an improved means for amplifying the sounds 30 produced by stringed instruments which is a relatively simple yet durable construction and which will suitably amplify the sounds without distortion.

With the foregoing and other objects in View, which will be made manifest in the following detailed description, and specifically pointed out in the appended claims, reference is had to the accompanying drawing for an illustrative embodiment of the invention, wherein:

Figure 1 is a plan view of a guitar to which the invention has been applied;

Fig. 2 is a longitudinal section through the body of the instrument;

Fig. 3 is a transverse section taken substantially upon the line 3-3 of Fig. 2 in. the direction indicated; and

Fig. 4 is a partial view in vertical section illustrating a slightly modified form of construction.

Referring to the accompanying drawing wherein similar reference characters designate similar parts throughout, I have illustrated the invention as having been applied to a guitar. The body of the guitar indicated at H], may be of any conventional or preferred construction and carries a fret board II. On the top of the instrument there is provided a suitable tail piece I2 carrying a transverse pivot. 13 which preferably is horizontally even with the strings [4. This pivot serves to pivotally mount a bridge-providing member 15 which is in the form of an angular lever, the top of which is widened as indicated at It and bent downwardly as at ll forming the bridge for the strings. The strings l4 extend toward the tail piece underneath bridge I! and their ends extend upwardly through perforations I8 where they are secured. The arrangement is such as illustrated in Fig. 2 that the tension on the strings i4 urges the bridge-providing member into a position wherein the bridge I! is in engagement with the strings. the bridge-providing member extends forwardly toward the fret board as indicated at l9 and is secured to a suitable amplifier or resonator 20. This resonator may be in the form of a conical paper cone or it may be formed of spun aluminum composition or any other suitable material. The particular shape of the resonator is not of great importance in the present invention. Where it is conical as shown, its base is disposed upwardly and its margin may be suitably secured to the underside of the top of the body ill. The open bottom of the cone may be covered by a suitable cover indicated at 2! which may be of fabric, perforated metal, or the like.

It will be appreciated that when the strings are plucked or bowed and are thus vibrated, that the vibrations of the strings will be transmitted to the pivoted bridge-providing member which pivots around pivot l3 as a center. As this bridge-providing member is in the form of an angular lever the magnitudes of the vibrations at the end of arm 19 will be magnified or amplified and thus transmitted to the resonator 20 which on being thus vibrated in accordance with the sound vibrations of the strings, will produce the sound materially amplified.

In Fig. 4 I have illustrated a slight modification wherein the bridge-providing member is pivoted as at 26 but the bridge indicated at 21 instead of being arranged over the strings 28 is disposed beneath them and is bearing upwardly. In this form of construction as before the ten.- sion of the strings is such as to cause the bridge 21 to be urged into firm engagement with the strings. The bridge-providing member- 25 is operatively connected to a suitable resonator (not shown) corresponding to resonator 29.

While I have shown the use of a single bridgeproviding member which provides a single bridge common to all strings, it will be appreciated that The lower end of 15 it is possible to provide separate bridge-providing members for each string and to operatively connect these individual bridge-providing members to the same or different resonators suitably mounted within the body of the instrument.

In both forms of construction illustrated herein it will be noted that the ends of the strings extend from the bridge across the line joining the bridge and the pivot. With this arrangement the tension of the strings urges the bridge providing member to rotate about its pivot in such a direction as to cause the bridge to engage the strings.

It is not necessary in all instances that the bridge-providing member be connected directly to the resonator. In some instances it may be desirable or necessary to interpose a pivoted lever between the resonator and the bridge-providing member so that the bridge-providing member vibrates one end of the pivoted lever and the other end of the lever is connected to the resonator. Also, it is not necessary in all instances that the vibrations of the strings I 4 be transmitted mechanically to the resonator. In some instances it may be desirable to connect the bridge-providing member to an electrical pick-up which converts the vibrations transmitted to the bridgeproviding member into electric currents which, in turn, are converted into sound through a loud speaker which may be incorporated in the body of the instrument or in a separate case.

From the above-described construction, it will be appreciated that an improved amplifying stringed instrument is provided which is of relatively simple and durable construction and which will advantageously serve to amplify the sounds of the instrument materially. The sound produced by the resonator is brought about without distortion so as to not only amplify the instrument but to produce tones of pleasing quality.

Various changes may be made in the details of construction without departing from the spirit or scope of my invention as defined in the appended claims.

I claim:

1. In a string-ed instrument, pivoted means to which the strings are connected, and means providing a bridge on said pivoted means urged by the tension of the strings into engagement with the strings.

2. In a stringed instrument, pivoted means to which the strings are connected, and means providing a bridge on said pivoted means urged by the tension of the strings into engagement with the strings, and means operatively connected to the pivoted means for amplifying the sound vibrations transmitted thereto.

3. In a stringed instrument, a pivot arranged transversely to the length of the strings of the instrument, bridge-providing means pivoted thereto, the strings being connected, to said means between the bridge and the pivot and across the line between the bridge and the pivot whereby the tension of the strings urges the bridge of the bridge-providing member into engagement with the strings,

4. In a stringed instrument, a pivot arranged transversely to the length of the strings of the instrument, bridge-providing means pivoted thereto, the strings being connected to said means between the bridge and the pivot and across the line between the bridge and the pivot whereby the tension of the strings urges the bridge of the bridge-providing member into engagement with the strings, and means operable by vibration of the bridge-providing member for amplifying sound vibrations transmitted thereto by the strings.

5. In a stringed instrument, a pivot arranged transversely to the length of the strings of the instrument, bridge-providing means pivoted thereto, the strings being connected to said means between the bridge and the pivot and across the line between the bridge and the pivot whereby the tension of the strings urges the bridge of the bridge-providing member into engagement with the strings, an arm carried by the bridgeproviding member which is of greater length than the distance between the pivot and the bridge,

whereby the tension of the strings urges the bridge of the bridge providing member into engagement with the strings, an arm carried by the bridge providing member, said arm being operatively connected to the amplifier so as to cause the amplifier to amplify sound vibrations transmitted from the bridge through said arm.

RALPH W. ROBERTSON. 

